At the same time, even applying the alternative method from [1]}, we are not able to find an explicit form of the roots of the Lopatinski determinant. Instead of this, motivated by [2]}, we analyze the transition between uniform and weak stability (still using the alternative definition of the uniform Lopatinski condition from [1]}). It turns out that in the space of admissible parameters of the unperturbed flow this transition coincides exactly with the boundary of the parameter domain of uniform stability found in [4]} by the energy method. Moreover, we show that the rectilinear shock waves are never violently unstable (this was not proved in [4]}). The latter is natural because from the physical point of view the elastic force should play stabilizing role and we know that shock waves in isentropic gas dynamics [6]} are also either uniformly or weakly stable.
